Seinfeld- Jerry and Elaine are exes and breify get back together at the end of season one
Friends- lots of romantic entaglements but mainly Chandler/Monica, Ross/Rachel, and Joey/Rachel
How I Met Your Mother - two of the main characters are a steady couple, the other three are a love triangle
Big Bang Theory- by the end, it’s three couples and one single guy
Any shows like these where the main characters never date each other or hook up with each other?
Probably not, because romantic entanglements make for better TV.
Very subjective. In my opinion introducing romantic subplots is the laziest of writing.